The present invention relates to strapping machines designed to apply a bundling strap to a large package and, in particular, to an apparatus for applying edge protectors to the edges of the package prior to the application of strapping thereabout.
In order to facilitate the handling of large objects or a plurality of objects, it is often desirable to cause a strap to be placed about the object or to create a package by strapping together a plurality of objects. As used herein "package" is intended to refer to either a single object or a multiplicity of objects either previously joined or to be joined by strapping. In addition, "strap" or "strapping" applies equally to metal or non-metal strap of generally rectangular cross section or oval-shaped or circular wire or any other material suitable for binding a package.
Typically, such straps are applied under a considerable degree of tension and, often, the package is of a nature which renders it advantageous to compress the package prior to applying strapping thereto. Obviously, if a package is compressed and a strap is applied under tension, when the compressive force is released, additional tension will be created in the strap.
It must be appreciated that when such a tension is present in the encircling strapping, the edge or corner areas of the package are vulnerable to damage by the strapping. Such damage may occur in various ways. For example, the edge areas may be damaged by impressions caused by the strapping. Also, if a metal strap is utilized, it will be subject to corrosion which would likely stain or otherwise disfigure the package. It is notable that in some applications, especially in the lumber industry, if any of the package of lumber is damaged, the price receivable for the entire package may be substantially decreased. As such, it is desirable to place edge protectors on the edges of the package which will be in contact with the strapping prior to the application thereof.
Such edge protectors may consist of metal, plastic, fibrous or other material capable of distributing the localized force caused by the strapping on the edge of the package. The edge protectors typically utilized have a concave face configured to conform to the edge to be protected. Recently, in certain applications, it has become particularly advantageous to utilize fibrous or hard cardboard edge protectors having two legs and an included angle of approximately ninety degrees (90.degree.). One advantage of such an edge protector is that that type of edge protector is usually lowest in cost per unit. Also, such protectors do not themselves tend to damage by impression or otherwise the package edge areas as may occur with metal or plastic edge protectors. Moreover, cardboard edge protectors do not corrode and thereby stain the package surface.
Previously, edge protectors were placed on the package corners by hand. Obviously, such a practice was labor intensive, and thus costly, slow and dangerous. In addition, prior mechanized edge protector applicators have proven expensive and readily susceptible to jamming or misplacement, especially with respect to fibrous edge protectors. Also, regarding fibrous corner protectors, as they frequently expand in thickness up to 80% and the included angle often varies, prior means of application have proven inadequate to accommodate such a change in thickness. Moreover, as a great range of angular variations is present in the fibrous edge protectors, an additional problem is presented.
The subject invention is directed toward an improved apparatus for edge protector application which overcomes, among others, the above-described problems and provides an effective, efficient device for accurately positioning edge protectors on the edges of a package to which strapping is to be applied.